Textbook Question
Compare conservative, semiconservative, and dispersive modes of DNA replication.
Ch. 11 - DNA Replication and Recombination
Klug12th EditionConcepts of Genetics ISBN: 9780135564776
Not the one you use?Change textbookSelect a different textbook
Table of contents
- Ch. 1 - Introduction to Genetics17
- Ch. 2 - Mitosis and Meiosis36
- Ch. 3 - Mendelian Genetics51
- Ch. 4 - Extensions of Mendelian Genetics74
- Ch. 5 - Chromosome Mapping in Eukaryotes51
- Ch. 6 - Genetic Analysis and Mapping in Bacteria and Bacteriophages46
- Ch. 7 - Sex Determination and Sex Chromosomes33
- Ch. 8 - Chromosome Mutations: Variation in Number and Arrangement40
- Ch. 9 - Extranuclear Inheritance31
- Ch. 10 - DNA Structure and Analysis43
- Ch. 11 - DNA Replication and Recombination44
- Ch. 12 - DNA Organization in Chromosomes30
- Ch. 13 - The Genetic Code and Transcription54
- Ch. 14 - Translation and Proteins47
- Ch. 15 - Gene Mutation, DNA Repair, and Transposition41
- Ch. 16 - Regulation of Gene Expression in Bacteria29
- Ch. 17 - Transcriptional Regulation in Eukaryotes41
- Ch. 18 - Post-transcriptional Regulation in Eukaryotes33
- Ch. 19 - Epigenetics33
- Ch. 20 - Recombinant DNA Technology44
- Ch. 21 - Genomic Analysis36
- Ch. 22 - Applications of Genetic Engineering and Biotechnology36
- Ch. 23 - Developmental Genetics37
- Ch. 24 - Cancer Genetics34
- Ch. 25 - Quantitative Genetics and Multifactorial Traits54
- Ch. 26 - Population and Evolutionary Genetics45
Chapter 11, Problem 4
Describe the role of ¹⁵N in the Meselson–Stahl experiment.
Verified step by step guidance1
Understand that the Meselson–Stahl experiment was designed to determine the mechanism of DNA replication, specifically whether it is conservative, semi-conservative, or dispersive.
Recognize that ¹⁵N (nitrogen-15) is a heavy isotope of nitrogen used to label the DNA of bacteria by growing them in a medium containing ¹⁵N, which gets incorporated into the nitrogenous bases of DNA.
Note that after several generations in ¹⁵N medium, the DNA becomes 'heavy' due to the incorporation of ¹⁵N, allowing it to be distinguished from 'light' DNA containing the more common ¹⁴N isotope by density gradient centrifugation.
Observe that when bacteria are transferred from ¹⁵N medium to ¹⁴N medium and allowed to replicate, the distribution of DNA densities after replication can be analyzed to infer the replication mechanism.
Conclude that the role of ¹⁵N is to serve as a molecular marker that enables the separation and identification of DNA molecules based on their density, which is critical for interpreting the results of the Meselson–Stahl experiment.
Verified video answer for a similar problem:
This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
1mWas this helpful?
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Isotopic Labeling with ¹⁵N
¹⁵N is a stable heavy isotope of nitrogen used to label DNA molecules. In the Meselson–Stahl experiment, bacteria were grown in a medium containing ¹⁵N, causing their DNA to incorporate this heavier isotope, which allowed differentiation between old and new DNA strands based on density.
Recommended video:
Guided course
05:34
Bacteriophage Regulation
Density Gradient Centrifugation
This technique separates molecules based on their density by spinning them in a cesium chloride gradient. DNA containing ¹⁵N is denser and forms a distinct band lower in the gradient compared to DNA with the lighter ¹⁴N, enabling visualization of DNA replication patterns.
Recommended video:
Guided course
03:52Cell-cell interactions
Semiconservative DNA Replication
The Meselson–Stahl experiment demonstrated that DNA replication is semiconservative, meaning each new DNA molecule consists of one old (¹⁵N-labeled) strand and one newly synthesized (¹⁴N) strand. The use of ¹⁵N allowed tracking of parental and daughter strands to confirm this model.
Recommended video:
Guided course
14:31Semiconservative Replication
Related Practice
Textbook Question
What are the requirements for in vitro synthesis of DNA under the direction of DNA polymerase I?
Textbook Question
In the discussion, we focused on how DNA is replicated and synthesized. We also discussed recombination at the DNA level. Along the way, we encountered many opportunities to consider how this information was acquired. On the basis of these discussions, what answers would you propose to the following fundamental questions?
What observations reveal that a 'telomere problem' exists during eukaryotic DNA replication, and how did we learn of the solution to this problem?
Textbook Question
Write a short essay that distinguishes between the terms replication and synthesis, as applied to DNA. Which of the two is most closely allied with the field of biochemistry?
4
views
Textbook Question
In Kornberg's initial experiments, it was rumored that he grew E. coli in Anheuser-Busch beer vats. (Kornberg was working at Washington University in St. Louis.) Why do you think this might have been helpful to the experiment?
Textbook Question
Predict the results of the experiment by Taylor, Woods, and Hughes if replication were
(a) conservative and
(b) dispersive.
7
views